Microstructure and Corrosion Behavior of Hot-Deformed and Cold-Strained High-Mn Steels

Abstract

The electrochemical corrosion properties of 26Mn-3Si-3Al and 27Mn-4Si-2Al austenitic steels in two different states were studied in 0.1 M H 2 SO 4 and 3.5% NaCl using potentiodynamic polarization tests. The effect of cold deformation on the microstructure and corrosion behavior of steels was analyzed. In acid solution, both steels exhibited lower corrosion resistance than in chloride solution independently on the steel state (hot-rolled, cold-worked). Cold deformation decreases the corrosion resistance, though this effect is smaller than the effect of chemical composition related to the combined Al + Si addition. All steels showed the evidence of pitting corrosion. The intensive dissolution of Fe and Mn takes place in the acid medium.

Corrosion Resistance and Pitting Behaviour of Low-Carbon High-Mn Steels in Chloride Solution

“…Better corrosion resistance of the X6MnSiAlNbTi26-3-3 steel is attributed to higher Al and lower Si contents in comparison to the X4MnSiAlNbTi27-4-2 steel (Table 1). It confirms our earlier results of potentiodynamic polarization tests [14,21]. It is well known, that aluminium improves corrosion resistance of steel due to its tendency to formation of the protective Al 2 O 3 passive layer on the steel surface in solutions of pH about 7 (Pourbaix diagrams), which increased slightly the corrosion resistance of the investigated steel [22].…”

“…Results of potentiodynamic polarization tests conducted in 3.5% NaCl solution, showed that the thermomechanically treated X4MnSiAlNbTi27-4-2 steel specimens are characterized by higher corrosion current density (0.09 mA/ cm 2 ) in comparison to the thermomechanically treated X6MnSiAlNbTi26-3-3 steel (0.009 mA/cm 2 ). Corrosion current density of high-Mn steels is significantly higher in acidic solutions [14]. Similar results were collected for cold deformed steel specimens.…”

“…Additionally, the high amount of deformation twins and presence of elongated sulfide inclusions were identified. Results of our previous investigations [14] showed that both steels independently on their state (thermomechanically treated or cold worked) are characterized by the microstructure consisting of 100% austenite.…”

Strain Hardening Behavior and Microstructure Evolution of High-Manganese Steel Subjected to Interrupted Tensile Tests

“…No martensites ε or α' were observed in the investigated microstructure (Figures 3a-h and 4a-h). It was confirmed in our earlier research using X-ray diffraction [8]. Such behavior is typical for steels characterized by an SFE >20 mJ/m 2 , resulting from the chemical composition.…”

“…The martensite platelets and mechanical twins act as obstacles to dislocation motion and block the movement of dislocations, and in this way they affect the work hardening behavior of high-manganese steels. The mentioned microstructural effects determine the mechanical behavior of steel, resulting in the delay of local necking, which allows for large uniform elongations [6][7][8][9][10][11].…”